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{{Short description|Absolute temperature scale using Fahrenheit degrees}}
{{About|the temperature scale|the idealized thermodynamic cycle for a steam engine|Rankine cycle|the scale measuring recovery after stroke|Modified Rankin Scale}}
{{Infobox unit
| name          = Rankine
| quantity      = [[Temperature]]
| symbol        = R
| symbol2       = °R
| symbol3       = °Ra
| namedafter    = [[Macquorn Rankine]]
| calcinput     = {{calculator|id=r|type=number|default=491.67|size=6}}
| units1        = [[Kelvin scale]]
| inunits1      = {{calculator|type=plain|formula=round(5*r/9,2)|NaN-text=?|default=273.15}}&nbsp;K
| units2        = [[Celsius scale]]
| inunits2      = {{calculator|type=plain|formula=round(5*r/9-273.15,2)|NaN-text=?|default=0}}&nbsp;°C
| units3        = [[Fahrenheit]]
| inunits3      = {{calculator|type=plain|formula=round(r-459.67,2)|NaN-text=?|default=32}}&nbsp;°F
}}

The '''Rankine scale''' ({{IPAc-en|ˈ|r|æ|ŋ|k|ɪ|n}} {{respell|RANG|kin}}) is an [[absolute scale]] of [[thermodynamic temperature]] named after the [[University of Glasgow]] [[engineer]] and [[physicist]] [[Macquorn Rankine]], who proposed it in 1859.<ref name="Merriam-Webster"/>

== History ==
Similar to the [[Kelvin|Kelvin scale]], which was first proposed in 1848,<ref name="Merriam-Webster">{{Cite Merriam-Webster|Rankine|access-date=2019-11-07}}</ref> zero on the Rankine scale is [[absolute zero]], but a temperature difference of one Rankine degree (°R or °Ra) is defined as equal to one [[Fahrenheit]] degree, rather than the [[Celsius]] degree used on the Kelvin scale. In converting from kelvin to degrees Rankine, 1&nbsp;K = {{sfrac|9|5}}&nbsp;°Ra or 1&nbsp;K = 1.8&nbsp;°Ra. A temperature of 0&nbsp;K (−273.15&nbsp;°C; −459.67&nbsp;°F) is equal to 0&nbsp;°Ra.<ref name="SP811">[https://www.nist.gov/physical-measurement-laboratory/nist-guide-si-appendix-b8 B.8 Factors for Units Listed Alphabetically] from {{harvnb|Thompson|Taylor|2008|pp=45–69}}</ref>

== Usage ==
The Rankine scale is used in engineering systems where heat computations are done using degrees Fahrenheit.<ref name="arstechnica">{{cite web |url=https://arstechnica.com/science/2022/08/warning-sign-nasa-never-finished-a-fueling-test-before-todays-sls-launch-attempt/ |title=Warning sign? NASA never finished a fueling test before today's SLS launch attempt |work=Ars Technica |first=Eric |last=Berger |date=2022-08-29 }}</ref>

The symbol for '''degrees Rankine''' is °R.<ref name="SP811" /> However, historical texts referring to "°R" are much more likely to mean the historically quite common [[Réaumur scale]].<ref>[[Réaumur Scale]]</ref> As there is also the [[Rømer scale]], it is better to use °Ra to be unambiguous. By analogy with the SI unit [[kelvin]], some authors term the unit ''Rankine'', omitting the degree symbol.<ref name="dummies">{{harvnb|Pauken|2011|page=20}}</ref><ref name="engineering">{{harvnb|Balmer|2011|page=10}}</ref> 

Some temperatures relating the Rankine scale to other temperature scales are shown in the table below.
{|class="wikitable" style="text-align:right"
! colspan="2" rowspan="2" |
! colspan="5" |Scale
|-
! scope="col" | Kelvin
! scope="col" | Rankine
! scope="col" | Fahrenheit
! scope="col" | Celsius
! scope="col" | Réaumur
|-
! rowspan="4" |Temperature
! scope="row" | [[Absolute zero]]
| 0&nbsp;K
| 0&nbsp;°Ra
| −459.67&nbsp;°F
| −273.15&nbsp;°C
| −218.52&nbsp;°Ré
|-
! scope="row" | Freezing point of [[brine]]{{efn|The freezing point of [[brine]] is the zero point of Fahrenheit scale, old definition, see: {{harvnb|Grigull|1986}}}}
| 255.37&nbsp;K
| 459.67&nbsp;°Ra
| 0&nbsp;°F
| −17.78&nbsp;°C
| −14.224&nbsp;°Ré
|-
! scope="row" | Freezing point of water{{efn|The ice point of purified water has been measured to be 0.000089(10) degrees Celsius – see {{harvnb|Magnum|1995}}}}
| 273.15&nbsp;K
| 491.67&nbsp;°Ra
| 32&nbsp;°F
| 0&nbsp;°C
| 0&nbsp;°Ré
|-
! scope="row" | [[Boiling point]] of water{{efn|For [[Vienna Standard Mean Ocean Water]] at one [[Atmosphere (unit)|standard atmosphere]] (101.325&nbsp;kPa) when calibrated solely per the two-point definition of thermodynamic temperature. Older definitions of the Celsius scale once defined the boiling point of water under one standard atmosphere as being precisely 100&nbsp;°C. However, the current definition results in a boiling point that is actually 16.1&nbsp;mK less. For more about the actual boiling point of water, see [[Vienna Standard Mean Ocean Water#VSMOW in temperature measurement|VSMOW in temperature measurement]].}}
| 373.1339&nbsp;K
| 671.64102&nbsp;°Ra
| 211.97102&nbsp;°F
| [[Celsius#Melting and boiling points of water|99.9839&nbsp;°C]]
| 79.98712&nbsp;°Ré
|}

== See also ==
* [[Outline of metrology and measurement]]
* [[Comparison of temperature scales]]

== Notes ==
{{notelist}}

== References ==
{{reflist}}

== Bibliography ==
* {{cite book |last=Balmer |first=Robert |year=2011 |title=Modern Engineering Thermodynamics |location=Oxford |publisher=Elsevier Inc. |isbn=978-0-12-374996-3 }}
* {{Cite journal |last=Magnum |first=B.W. |date=June 1995 |title=Reproducibility of the Temperature of the Ice Point in Routine Measurements |url=http://www.cstl.nist.gov/div836/836.05/papers/magnum95icept.pdf |url-status=dead |journal=NIST Technical Note |volume=1411 |archive-url=https://web.archive.org/web/20070307055524/http://www.cstl.nist.gov/div836/836.05/papers/magnum95icept.pdf |archive-date=2007-03-07 |access-date=2007-02-11 }}
* {{Cite book |title=Thermodynamics For Dummies |last=Pauken |first=Michael |publisher=Wiley Publishing Inc. |year=2011 |isbn=978-1-118-00291-9 |location=Indianapolis }}
* {{Cite journal |url=https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication811e2008.pdf |title=Guide for the use of the International System of Units (SI) |last1=Thompson |first1=Ambler |last2=Taylor |first2=Barry N. |date=2008 |language=en |doi=10.6028/nist.sp.811e2008 |access-date=2019-11-07 |journal=NIST Special Publication |volume=811 }}
* {{Cite conference |last=Grigull |first=Ulrich |year=1986 |url=http://www.aihtc.org/pdfs/IHTC-8-Grigull.pdf |title=Heat Transfer |language=en |access-date=2022-08-29 }}

== External links ==

{{Scales of temperature}}
{{Portal bar|Energy}}

[[Category:Scales of temperature]]
[[Category:1859 introductions]]